A128754 - OEIS

%I #4 Nov 11 2010 07:34:06

%S 4,3,6,9,8,11,1,2,12,15,16,13,18,7,5,21,30,23,22,17,19,25,10,27,34,29,

%T 32,31,20,24,36,37,42,39,46,47,33,26,35,41,44,43,28,53,48,51,50,49,62,

%U 55,56,61,66,38,14,59,52,45,68,63,40,67,64,57,72,71,70,73,74,77,80,79

%N Permutation of positive integers obtained by swapping n-th natural number with the (n-g)-th sequentially, where g=prime(n+1)-prime(n)-1.

%C By numerical explorations up to 50k terms, it seems to be an "infinite braid", i.e. it consists of a single infinite cycle, without any fixed points or closed cycles.

%H Ferenc Adorjan, <a href="/A128754/b128754.txt">Table of n,a(n) for n=1..10000</a>

%o (PARI) {pperm(n)= /* Returns a vector with n terms of the sequence */

%o local(m,q,v,x,j,ap);j=n+prime(n+6)-prime(n);v=vector(j);x=vector(n);

%o for(i=1,j,v[i]=i);for(i=1,j,ap=prime(i+1)-prime(i)-1;q=v[i];v[i]=v[i-ap];v[i-ap]=q);

%o for(i=1,n,x[i]=v[i]);return(x)}

%Y Inverse of A128755, Cf. A128756, A128757.

%K nonn

%O 1,1

%A Ferenc Adorjan (fadorjan(AT)freemail.hu or ferencadorjan(AT)gmail.com), Mar 24 2007